Why is Pluto not a planet? For more than 70 years Pluto was recognized as one of the nine planets which was discovered by Clyde Tombaugh in 1930. But at a point in early 2000, astronomers began to deliberate seriously about whether Pluto was a planet or just a dwarf planet.
The long debate started when the assumed 10th planet was discovered. Eris was like Pluto, icy and all, but it was larger than Pluto. Now, why is Pluto not a planet?
International and astronomical union [IAU] decided to define what a planet really is. Pluto would still be a planet if it had fit into the 3 definitions that made a planet.
- Firstly, a planet needs to be in orbit around the sun
- It should have gravity strong enough to pull it in a spherical shape
- A planet needs to have a clear neighbourhood of its orbit
Yes, Pluto orbit around the sun and it has a very dominant gravity that made it spherical in shape. Pluto beat the first two definitions but didn’t beat the third. The third said that a planet must have “a cleared neighbourhood of its orbit “, this simply means that a planet should have a clear space. A planet should be able to consume smaller objects or eject them out with its gravity.
Because Pluto didn’t meet the third criteria so it was demoted to dwarf planet.
There would have been 100 more planets had the definition not come in place.
That would have been a messed up thing if we had about a 100 planet orbiting around our solar system.
- Small in size: Pluto is very small in size compared to other planets, it measures about half the width of the United States which is about 2,380 km wide.
- Far from Sun: Due to the distance between Pluto and Sun, the temperature is very cold of about -240 degree Celsius. From Pluto, the sun is the brightest star visible.
- Named by a child: The name Pluto was giving to this planet by an 11-year-old schoolgirl, Venetia Burney in 1930.
- Visitation to Pluto: The only spacecraft to visit Pluto is New Horizons mission by NASA, which passed close by in July 2015.
- Long Journey: It takes 248 Earth years for Pluto to complete it’s 1 year.
- Moon: There are 5 moons in Pluto. The largest, Charon, is so big that Pluto and Charon orbit each other like a double planet.
But now Pluto is no more regarded as a planet again.